Low water flow on forward a/c

Mightychan

Mightychan

Member
Oct 8, 2016
157
Panama City FL
Boat Info
2005 DA 420, AB Dink
Engines
Cummins 6CTA
This weekend my forward ac unit seemed to be struggling. Main cabin ac is cooling great and I have strong wster flow out of the port midships through hull. But I just have a trickle coming out of the front through hull. Where should I start looking for blockages? The sea strainer is clean. Thanks all!
 
I had the same situation except mine would trip the breaker after a few minutes of running with very low water flow coming out the thru Hull. Ended up being air in the intake line.
 
You’ll have these problems from time to time. I just had one this past weekend with the A/C unit on my bridge - which has a separate pump and waterline from the other A/C systems.

What you want to do is make a simple adapter that screws onto the end of your dockside water hose and fits into the A/C water line. In my case it’s a plastic taper with garden hose threads on one end. Gently turn up water pressure until you blow the gunk out the other end. In my case this weekend, I had some gunk in the line between the seacock and the strainer. 10 minute fix.
 
Chan,

Given your location, the blockage is scattered all throughout the cooling water line from the pump to the outlet on the side of the boat. You have just accumulated marine growth in the line. Running dockside freshwater at full pressure thru the cooling lines will help but probably won't totally fix the problem. In this area, thanks to the warm Gulf salt water, you usually need to clean the cooling lines with acid about once a year. I have written up the procedure we use a couple of times. I'll look for it in the morning and will post it if I have a copy with me.
 
Thanks all. Frank, I found your write up about mixing up an acid solution in a bucket and introducing it into the lines . Simple enough. What I did not see was the acid you were referring to. Would it just be a weak muratic acid mix? Also, any idea what size hoses I should expect? I can grab some fittings at Lowe's on my way to the slip . Many thanks!
 
Chan, you can go through all that initially if you want to, but personally I’m a believer in starting simple and working up. Why rebuild the engine if all you need is new spark plugs?

I was prepared to have to go high tech on my A/C this weekend, but starting with a good blow-out had me up on the bridge in comfy A/C sipping an ice tea in under 15 minutes. If it works for you, you’ll have cool A/C operating while you run to the hardware store for all components for a future acid flush.
 
I get silt in my lines that causes the forward unit’s water flow to diminish.

I have great pressure at my marina and periodically blast the lines out. It’s amazing what comes out.
 
Acid: a 50% muriatic acid solution will work, but I don't like to use it in anything that has solder joints in it like heat exchangers and A/C cooling coils because muriatic acid can attack and weaken the solder.

I use a product called Prep N Etch by Klean Strip and Home Depot carries it in t he paint department for about $16/gal.

https://www.homedepot.com/p/Klean-Strip-1-gal-Phosphoric-Prep-and-Etch-GKPA30220/100406369


Fittings: The plumbing on each boat is different, but the threaded fittings to the sea strainer on the 450DA are 3/4". I put a bronze "T" in the line from my A/C seacock to the sea strainer then plumbed a ball valve, a garden hose fittings and a quick-connect fitting to accept a mating quick connect on the hose from a bucket. the acid solution goes in the bucket which is hung above the a/c sea strainer. Close the seacock start up the A/C pump and "feed" the acid solution into the system. When the bucket is empty, shut off the A/C and wait about 10 minutes. Then connect the water hose to the quick-connect and turn on the water. It will flush the dead barnacles, shells and sea worms out of the system.

Once you get the plumbing done, you can try flushing the system with freshwater first to see if silt is the issue, but your boat is in deep enough water that silt is unlikely. The more likely cause is hard growth and lime deposits which isn't going to flush out.

Hope that helps..........
 
It's funny that even though I just got the boat, I seem to have all the same issues after 2 weeks as everyone else.

And I notice that the same people have the technical knowledge on it all which is unreal!! That's awesome.

Having a similar issue with the Forward Stateroom where the TStat blinks HI PS and basically shuts down.

I'm sure the unit needs to be cleaned and the system hasn't been flushed in forever.

I've attached the Air Conditioning System Diagram. Where do you blow out the system from?
 

Attachments

  • 2005 Sea Ray 50DB AC Diagram.pdf
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HI PS is definitely due to lack of sea water circulation.

If you want to blow it out with high pressure water, I suggest you pull the white hose off the three port manifold that is indicated for the forward A/C and connect shore water to it.

I’m not sure on Franks acid wash concept because it seems to me that most, if not all, of the solution will migrate through the units that aren’t plugged, and you’ll get very little if any solution in the plugged line.
 
Jeff,

the one to the common drain to the sump or both?

this is how I see it working. water comes in through the seacock, gets pumped to the a/c units then gets dumped out to the common drain and/or the sump, depending on which a/c unit. looks like the fwd stateroom a/c unit is the only one that gets dumped to both the sump and the common drain..

thanks again for all the help!

Steve
 
now that I read the diagram again....

Jeff are you saying to run the water through the manifold that goes through the a/c unit?

Do I need to have the a/c unit on while doing it?
 
There's an alternative scenario you should consider if blowing/cleaning out the lines doesn't help or perhaps as a first check. Last weekend I fired up the AC on arrival at the boat and pretty quickly got "HI PS" shutdowns on three of four units serviced by a single seawater pump with each having a separate overboard. The two amidships overboard discharges had no flow but the aft and forward ones had reduced flow. I cleaned the strainer (which was pretty clear) and blew out the system with air using my "Sea Flush" which will blow air through each unit and the seacock as well. The amidships flow was no better and forward stopped. I thought I was looking at a new pump/rebuild and/or figuring out how to clear the lines to each unit. A dock mate saw me at work and said he had had the same problem and that it had been a mostly clogged seacock. He fixed his by taking off the strainer hose and poking at the blockage (and eventually creating a geyser in the bilge). I've fortunately got a regular diver I called in. Sure enough, the intake was gunked up enough to constrain the flow to all but the lowest unit and all is working fine after the diver did his thing. I actually think my hull may have rested in the mud due to low water levels at some point.
 
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In your diagram, remove the line with the “23” pointing at it (that says forward stateroom) and connect to dock water. The water will travel through the unit and out the common drain. You can turn the forward A/C on while doing the flush, and it will work if you are getting water through the blockage or manage to blow it out. The line in your diagram that drains to the sump is actually your condensation drip pan.

As I recall on my previous 500DB, the three lines coming off the pump manifold are written on with marker. Make sure you pull the one labeled Fwd strm. Oh, by the way, make sure you close the seacock before you pull the line off the manifold!
 
Just a tip, I'd pull the lines from your unit and proceed to force water from there. The exit will either be the thru hull or the bilge (don't forget to disconnect the bulge end of the line from the manifold. Could be inside the unit or the manifold too. I hate knowing I couldbe sending crud into my unit (only going out will make its way through.

I got a spare pump, some old garden hose, a few clamps and fittings, a 5gal bucket and circulate hot water through the unit and or lines. If that doesn't work, I move to acid.
 
One word of caution when blowing your lines out. I did this and had the line separate from the ac unit even though the connection was double clamped. Dumped a bunch of water ( mostly fresh) into my aft cabin area. Since the boat was new to me I have no idea if the clamps were tight, but the lesson is check you connections while doing this.
 
you guys are the best!!!

Love this forum.....

maybe next week I do a major engine overhaul by myself with everyone's feedback....just kidding
 
So. Followed everyone’s advice and flushed all the lines today.

Shit everywhere.

Started at the manifold and tried to flush the stateroom system and it didn’t go anywhere. So I flushed it from the unit back to the manifold. Actually found a mussel shell the size of my pinky finger tip at the water inlet of the unit.

Was able to flush all the other lines with a little better results.

Although I can tell you my 15 year old son got tired of taking videos from either the port or starboard side showing me the flow of exit water

Flushed everything til it was clear, but I’m not convinced I’m done. Might purchase a ridlyme marine flush system and flush again....clearly this has never been done.

So I’m open to comments as you guys are the best...

Steve
 
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